There's no penetration to hide, it's simulated. For simulating oral sex on a woman, a lot of times they put protective guards over the girl's pussy which are blocked by the actor's face. As for the cum shot, it was a mixture of conditioner and Cetaphil that they used to simulate semen. You can find an article about it here: http://www.revelist.com/feminism/girls-deleted-sex-scene/6719